The present invention relates to automotive fuel injection systems, and in particular to a system for improving fuel pressure control in such systems.
Modern high-pressure fuel injection systems use a pump that provides high-pressure fuel to a fuel rail for distribution to fuel injectors. Positive displacement pumps are often used, and such pumps typically provide pressure spikes in the pressurized fuel supply to the fuel rail. Such spikes can have an adverse impact on the precision with which the fuel injectors meter fuel into the engine.
Furthermore, in the event an automotive engine is not used for a substantial time period, leakage in the pump and/or one or more injectors can reduce pressure in the fuel rail undesirably. In this case, it will typically take some time for pressure to be restored in the fuel rail, and engine starting may be adversely affected during this time.
The present invention is directed to an improved fuel pressure control system that largely overcomes the disadvantages described above.
By way of introduction, the preferred embodiment described below provides a pressure spike attenuator in an automotive fuel injection system. This pressure spike attenuator is preferably installed between the pump and the inlet to the fuel rail, and the attenuator includes an expandable pressure vessel, preferably of the type that includes a corrugated side wall that facilitates volumetric expansion of the pressure vessel. This pressure vessel is provided with a spring force over a differential volume selected to be adequate to substantially attenuate pressure spikes in the pressurized fuel supplied by the pump.
The embodiment described below includes a solenoid valve that in the open state allows fuel from the fuel pump to move between the pump and the pressure vessel as well as between the pump and the fuel rail. When closed, valve isolates the pump from both the pressure vessel and the fuel rail. Additionally, when closed the valve isolates the pressure vessel from the fuel rail. In this state, leakage in the pump and/or the injectors may depressurize the fuel line between the pump and the pressure vessel as well as the fuel rail, but such leakage will not depressurize the pressure vessel. When it is desired to start the vehicle the valve is opened, and the pressurized fuel of the pressure vessel is instantaneously available to pressurize the fuel rail and provide prompt engine starting.
The foregoing paragraphs have been provided by way of introduction, and they are not intended to limit the scope of the following claims.